Utility
blackouts and brownouts are
facts of life. Industry publications
cite an average of 100 anomalies
in utility power per month.
The protection of sensitive
equipment by the usage of AC
stand alone UPS provides an
easy solution, but as this article
will show, this solution is
far from being either cost effective
or power efficient. An integrated
DC UPS (DUPS) offers a substantially
cheaper, more reliable and more
efficient solution. However,
this solution requires preplanning
and serious consideration at
the system design phase, while
its power needs and sensitivity
to power interruption must be
clearly defined.
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INTRODUCTION
On a daily basis and in thousands
of places around the world, personal
computers and workstations crash
due to utility failures or merely
a dip in their voltages. The crashes
cause loss of data and system malfunctions.
This results in a significant loss
of time required to restore the
information lost and to reset the
system. Industry publications cite
up to 100 utility malfunctions or
disturbances per month in the U.S.
In developing countries utility
power is poorly regulated and very
unpredictable – causing a
constant nightmare to computer users.
Mass providers
of telecommunication services and
cable TV (as well as multitudes
of other process-control industries)
face the same exact problem. Here
the problem results in the loss
of customers and revenues. In process-control,
a power failure could possibly cause
the loss of irreplaceable material
that would be destroyed if the operations
process were to be interrupted.
Imagine a blood analysis machine
losing 100 blood samples due to
a temporary malfunction caused by
a utility failure. The inconvenience
and wasted time to retake these
samples is almost unimaginable.
Now try to comprehend the crash
of a computer in a stock market
trading office or a busy airline
reservation system, and you will
quickly conclude that none of these
systems should be operated without
a power backup system which provides
instant power replacement to utility.
These backup systems are widely
known as a UPS (Uninterruptible
Power Source.) The length of backup
time that the UPS provides depends
on its rating, the capacity of its
internal batteries, and on the magnitude
of the load. Common backup time
offered by most standard UPSs ranges
between 5 minutes and 4 hours (but
for the most part it is 5-15 minutes.)
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